Sterol aminoacylation regulates conidiation and sclerotia formation in Aspergillus oryzae

Abstract

Ergosterol is a major fungal membrane component that contributes to membrane functions. We recently discovered novel ergosterol derivatives conjugated with amino acids, namely two aminoacylated ergosterols (Erg-aa), 1-ergosteryl-L-aspartate (Erg-Asp) and 1-ergosteryl-glycine (Erg-Gly), and the synthase involved (ErdS and ErgS, respectively). These enzymes are widely conserved in fungi belonging to the Dikarya subkingdom. However, the physiological role of Erg-aa remains unknown. Here, we report that Erg-aa are involved in conidiation and sclerotia formation in Aspergillus oryzae. The deletion of AoerdS or AoergS led to the reduction of conidia, accompanied by the downregulation of conidiation-regulating genes. In contrast, these deletants formed sclerotia considerably. AoerdS inducible strains also decreased conidia and promoted sclerotia formation under AoerdS suppressing condition, whereas the opposite morphology was observed under AoerdS inductive condition. We also investigated the effects of synthetic Erg-aa on fungal growth. Externally added Erg-Asp slightly promoted conidiation but did not affect sclerotia formation. On the other hand, Erg-Gly promoted the elongation of aerial hyphae and reduced both conidia and sclerotia. Finally, the deletion of AoerdS or AoergS altered susceptibility to ergosterol associating agents, indicating that ergosterol aminoacylation may change the physicochemical properties of ergosterol. Our findings expand the biological role of sterol modification in fungi.